JP2019503486A - Extended infrared spectroscopic ellipsometry system and method - Google Patents

Abstract

The present application discloses a method and system for performing simultaneous spectroscopic measurements of semiconductor structures at ultraviolet, visible and infrared wavelengths. In one embodiment, the wavelength error is reduced by setting the direction of chromatic dispersion on the detector surface to a direction perpendicular to the projection of the incident surface on the detector surface. In one embodiment, infrared wavelengths over a wide band are detected by a detector having a plurality of photosensitive areas that exhibit different sensitivity characteristics. The collected light is linearly dispersed on the detector surface according to the wavelength. Each of several photosensitive areas is arranged on the detector to be sensitive to a different incident wavelength range. In this way, infrared wavelengths over a wide band are detected with a high signal-to-noise ratio by a single detector. These features enable high throughput measurements with high throughput, accuracy and accuracy of high aspect ratio structures.

Description

  The described embodiments relate to metrology systems and methods, and more particularly to superior metrology methods and systems for three-dimensional semiconductor structures.

(Cross-reference to related applications)
This patent application is based on US Provisional Patent Application No. 62 / 279,469 dated January 15, 2016 entitled “Apparatus and Methods of Extended Infrared Ellipsometry”. Since this claim claims priority under the provisions of Article 119, the subject matter of the provisional patent application will be incorporated into the present application with this reference.

  Semiconductor devices such as logic devices and storage devices are typically manufactured by applying a series of processing steps to a specimen. The features and structural hierarchies of these semiconductor devices are formed by these processing steps. For example, lithography is one of the semiconductor manufacturing processes that envisage pattern generation on a semiconductor wafer. Other examples of semiconductor manufacturing processes include, but are not limited to, chemical mechanical polishing, etching, deposition, and ion implantation. A plurality of semiconductor devices may be formed on one semiconductor wafer and then divided into individual semiconductor devices.

  The metering process is a process used in various steps in the semiconductor manufacturing process, and thereby it is possible to detect defects on the wafer and promote yield improvement. Optical metrology techniques are expected to provide high throughput without the risk of sample destruction. Numerous optical metrology-based technologies, such as scatterometry and reflectometry equipment, and associated analysis algorithms, elucidate critical dimensions, film thickness, composition, overlay and other parameters of nanoscale structures Therefore, it is widely used.

  Flash memory architecture is changing from 2D floating gate architecture to all 3D geometry. In some examples, the film stack and etched structure are very deep (eg, the depth reaches 6 μm). Such a high aspect ratio structure causes difficulties in film measurement and CD measurement. The ability to measure critical dimensions and define the hole and trench shape of those structures is critical to achieving the desired performance level and device yield.

  Low signal-to-noise ratio (SNR) is a problem in many optical technologies, and only a small portion of the illumination light can reach the bottom of the high aspect ratio feature (feature) and reflect it up to the detector This is the cause. That is, there are many high-throughput weighing technologies that can be used, and CD and film measurement with a high aspect ratio structure cannot be performed reliably. Critical dimension small angle X-ray scatterometry (CD-SAXS), normal incidence reflectometry and scatterometry are being explored as metrology solutions for high aspect ratio structures, but development is still ongoing.

  A cross-sectional scanning electron microscope (SEM) is a destructive technique with low throughput and is not suitable for in-line weighing. Atomic force microscopes (AFMs) have poor high aspect ratio structure metrology capabilities and relatively low throughput. It is not yet clear whether CD-SAXS can achieve the high throughput capability required in the semiconductor industry. Model-based infrared reflectometry (MBIR) is used for metrology of high aspect ratio DRAM structures, but this technique does not provide the resolution that can be obtained at shorter wavelengths, and the measurement spot size is too large for semiconductor metrology. Not suitable. Please refer to Non-Patent Document 1 which is incorporated in this application as if there is a full explanation with this reference.

  Optical CD metrology currently presents a detailed profile of structures having depths and lateral dimensions on the μm scale, with relatively small spots (eg, less than 50 μm, more preferably less than 30 μm). It lacks the ability to measure with throughput. Patent Document 1 which is incorporated in the present application as if there is a full explanation with this reference describes an infrared spectroscopic ellipsometry (polarization analysis) technique suitable for elucidating the characteristics of a high aspect ratio structure. However, the technique described therein has problems that it takes a long measurement time to measure over ultraviolet and infrared wavelengths, the wavelength stability is low, and the infrared wavelength region during operation is narrow.

US Pat. No. 8,860,937 US Patent Application Publication No. 2013/0114085

"Measuring deep-trench structures with model-based IR," by Gostein et al., Solid State Technology, vol. 49, no. 3, Mar. 1, 2006

  In summary, difficult features are imposed on optical metrology systems as feature sizes shrink and structural features increase in depth. If the optical weighing system is not matched to high accuracy and accuracy requirements, the increasingly complex target cannot be weighed at high throughput and cost effective. In this context, broadband illumination and data collection speed, focus error and infrared wavelength range are critical performance constraints for designing optical metrology systems suitable for high aspect ratio structures. ing. Therefore, an excellent metering system and method that can overcome these limitations is desired.

  In this application, methods and systems for performing simultaneous spectroscopic measurements of semiconductor structures at ultraviolet, visible and infrared wavelengths are presented. Spectra including ultraviolet, visible and infrared wavelengths are measured at high throughput with the same alignment conditions. In this configuration, a machine error, for example, a wavelength error is corrected uniformly over the entire measurement wavelength. By simultaneously measuring targets with infrared, visible, and ultraviolet light within a single system, it is possible to precisely characterize complex three-dimensional structures. In general, a relatively long wavelength penetrates deeply into the structure, so that a structure having a relatively long pitch can be measured while suppressing high-order diffraction. At relatively short wavelengths, precise dimensional information is obtained for structures that are accessible at relatively short wavelengths (ie higher layers) and for relatively small CD and roughness features. Longer wavelengths are less sensitive to roughness, so increasing the wavelength according to certain examples allows measurement of the dimensional characteristics of a target having a relatively rough surface or interface.

  In one aspect, a fine focus sensor (FFS) is incorporated into the detection subsystem to provide a focus error correction measurement input during measurement.

  Further, in one aspect, the measurement spot is imaged on the detector, and the direction aligned with the incident surface on the wafer surface is oriented in a direction perpendicular to the wavelength dispersion direction on the detector surface. A broadband spectrometer system is constructed. With this arrangement, the sensitivity of the weighing system to focusing errors is greatly reduced. Since the sensitivity to focusing error is low, precise measurement results can be obtained with a shorter MAM time and thus with a higher throughput.

  In one embodiment, a multi-zone infrared detector that combines several sensitivity bands at different locations on a single detector package is employed in the metering system described herein. The detector is configured to provide a continuous spectrum of data with different sensitivities depending on the location of incidence. The collected light is linearly dispersed on the detector surface according to the wavelength. Each of several photosensitive areas is arranged on its detector to be sensitive to different incident wavelength ranges. In this configuration, infrared wavelengths over a wide area are detected with a high signal-to-noise ratio by a single detector.

  In a further aspect, the size of the illumination field projected onto the wafer plane along the direction perpendicular to the plane of incidence is adjusted based on the nature of the measured target so that the resulting measurement accuracy and speed are optimized.

  Since the above is a summary, simplifications, generalizations and omissions of detail are included everywhere; therefore, as will be apparent to those skilled in the art (so-called those skilled in the art), this summary is solely illustrative. It is something and not limited. Other aspects, inventive features and advantages of the devices and / or processes described herein will become apparent in the non-limiting detailed description set forth herein.

1 is a diagram illustrating an example 100 of a metrology system that performs simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths, according to one embodiment. FIG. FIG. 6 illustrates an example weighing system 200 that performs simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths according to another embodiment. FIG. 6 is a diagram illustrating an example 300 of a metrology system that performs simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths according to yet another embodiment. FIG. 6 is a diagram illustrating an example 400 of a metrology system that performs simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths according to yet another embodiment. FIG. 2 is a top view of a wafer 120 including an illustration of a measurement spot 116 illuminated by the illumination light beam 117 of FIG. It is a direct view of the surface of the detector 23 in the weighing system of the conventional configuration. FIG. 6 is a diagram showing the occurrence of a focus position error by the wafer 120. It is a figure which shows the condensed light beam which was wavelength-dispersed and imaged on the surface of the detector 23 by the conventional form. It is a direct view of the surface of the detector 141 shown in FIG. FIG. 2 is a direct view of the surface of the detector 150 shown in FIG. 1 according to one embodiment. FIG. 4 shows a typical photosensitivity curve for four available indium gallium arsenide (InGaAs) sensors. FIG. 6 illustrates a method 500 for performing simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible and infrared wavelengths in accordance with at least one aspect described herein. It is a figure which shows the example 600 of the high aspect ratio NAND structure in which the low translucency to a measurement object structure (group) becomes a problem.

  Reference will now be made in greater detail to background examples and certain embodiments of the invention, examples of which are illustrated in the accompanying drawings.

  In this application, methods and systems for performing simultaneous spectroscopic measurements of semiconductor structures at ultraviolet, visible and infrared wavelengths are presented. Spectra including ultraviolet, visible and infrared wavelengths are measured at high throughput with the same alignment conditions. In this configuration, a machine error, for example, a wavelength error is corrected uniformly over the entire measurement wavelength. In one embodiment, the wavelength error is reduced by setting the direction of chromatic dispersion on the detector surface to a direction perpendicular to the projection of the incident surface on the detector surface. In one embodiment, infrared wavelengths over a wide area are detected by a detector having a plurality of photosensitive areas that exhibit different sensitivity characteristics. The collected light is linearly dispersed on the detector surface according to the wavelength. Each of several photosensitive areas is arranged on the detector to be sensitive to a different incident wavelength range. In this configuration, infrared wavelengths over a wide area are detected with a high signal-to-noise ratio by a single detector. By each of these features or a combination thereof, high throughput measurement of a high aspect ratio structure (eg, a structure having a depth of 1 μm or more) can be performed with high throughput, accuracy, and accuracy.

  By simultaneously measuring targets with infrared, visible, and ultraviolet light within a single system, it is possible to precisely characterize complex three-dimensional structures. In general, a relatively long wavelength penetrates deeply into the structure, so that a structure having a relatively long pitch can be measured while suppressing high-order diffraction. At relatively short wavelengths, precise dimensional information is obtained for structures that are accessible at relatively short wavelengths (ie higher layers) and for relatively small CD and roughness features. Longer wavelengths are less sensitive to roughness, so increasing the wavelength according to certain examples allows measurement of the dimensional characteristics of a target having a relatively rough surface or interface.

  In certain embodiments, the semiconductor device spectrometer methods and systems described herein are applied to the measurement of high aspect ratio (HAR) structures, large lateral dimension structures, or both. In these embodiments, low translucency into the measurement target structure (group) is a problem for a semiconductor device having a HAR structure (eg, NAND, VNAND, TCAT, DRAM, etc.). It is possible to measure optical critical dimension (CD), film and composition for complex devices. The HAR structure is often provided with a hard mask layer for performing an etching process for the HAR. As used herein, the term “HAR structure” refers to any structure characterized by an aspect ratio that is greater than 10: 1 and can be as high as 100: 1 or higher.

  FIG. 1 shows an example 100 of a weighing system that performs simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths. The one or more structures include, for example, at least one HAR structure or at least one large lateral dimension structure. The weighing system 100 shown in FIG. 1 is configured as a broadband spectroscopic ellipsometer. In general, however, the metering system 100 can be configured as a spectroscopic reflectometer, scatterometer, ellipsometer, or any combination thereof.

  The metering system 100 includes an illumination source 110 that generates an illumination light beam 117 incident on the wafer 120. The illumination source 110 is a broadband illumination source that emits illumination light having ultraviolet, visible, and infrared spectra. In some embodiments, the illumination source 110 is a laser sustained plasma (LSP) light source (so-called laser driven plasma light source). The pump laser of this LSP light source may be a continuous wave or a pulse. A laser-driven plasma light source can supply a considerably larger number of photons over the entire wavelength range of 150 nm to 2000 nm than a xenon lamp. The illumination source 110 may be a single light source or a combination of a plurality of broadband or discrete wavelength light sources. The light generated by the illumination source 110 includes a continuous spectrum from ultraviolet to infrared (eg, vacuum ultraviolet to mid-infrared) or some portion of the continuous spectrum. In general, the illumination light source 110 may comprise any suitable light source, such as a supercontinuum laser light source, an infrared helium neon laser light source, an arc lamp, or the like.

  In a further aspect, the illumination light group is broadband illumination light having a wavelength region having a width of at least 500 nm. As an example of the broadband illumination light, there is one including a wavelength of less than 250 nm or a wavelength of more than 750 nm. In general, the broadband illumination light includes a wavelength of 120 nm to 3000 nm. In some embodiments, broadband illumination light including a wavelength of more than 3000 nm may be employed.

  The metering system 100 shown in FIG. 1 has an illumination subsystem configured to direct illumination light 117 to one or more structures formed on a wafer 120. The illumination subsystem in the figure includes a light source 110, one or a plurality of optical filters 111, a polarizing member 112, a field stop 113, an aperture stop 114, and an illumination optical system 115. By using one or a plurality of optical filters 111, the amount of light emitted to the illumination subsystem, the spectral output, or both can be controlled. In certain examples, one or more multi-zone filters are employed as the optical filter 111. Polarization member 112 generates the desired polarization state so that it is emitted from the illumination subsystem. The polarizing member according to certain embodiments is a polarizer, a compensator, or both, which can include any suitable commercially available polarizing member. The polarizing member may be a fixed type, a rotatable type that can be in several fixed positions, or a continuous rotating type. Although the illumination subsystem shown in FIG. 1 has one polarization member, the illumination subsystem may have a plurality of polarization members. Field stop 113 controls the field of view (FOV) of the illumination subsystem, which can include any suitable commercially available field stop. The aperture stop 114 controls the numerical aperture (NA) of the illumination subsystem, which can include any suitable commercially available aperture stop. Light from illumination source 110 is directed into illumination optical system 115 and focused onto one or more structures (not shown in FIG. 1) on wafer 120 by the illumination optical system. The illumination subsystem may be any type and arrangement of optical filter (s) 111, polarizing member 112, field stop 113, aperture stop 114 and illumination optics 115 known in the field of spectroscopic ellipsometry, reflectometry and scatterometry. It can have.

  The illumination light beam 117 shown in FIG. 1 passes through the optical filter (group) 111, the polarizing member 112, the field stop 113, the aperture stop 114, and the illumination optical system 115, and propagates as a beam from the illumination source 110 to the wafer 120. Go. The beam 117 illuminates a portion of the wafer 120 on the measurement spot 116.

  In a certain example, the beam size of the illumination light group 117 projected on the surface of the wafer 120 is smaller than the size of the measurement target measured on the surface of the specimen. Examples of beam shaping techniques are described in Wang et al. Is described in detail in U.S. Pat. No. 6,053,086, the entire contents of which are incorporated herein by reference.

  The metering system 100 also has a collection optics subsystem configured to collect light generated by the interaction between the one or more structures and the incident illumination beam 117. The condensed light beam 127 is condensed from the measurement spot 116 by the condensing optical system 122. The condensed light 127 passes through the condensing aperture stop 123, the polarizing element 124, and the field stop 125 of this condensing optical system subsystem.

  The condensing optical system 122 has some condensing element suitable for condensing from one or more structures formed on the wafer 120. The condensing aperture stop 123 controls the NA of the condensing optical system subsystem. The polarizing element 124 analyzes a desired polarization state. The polarizing element 124 is a polarizer or a compensator. The polarizing element 124 may be a fixed type, a rotatable type that can be in several fixed positions, or a continuous rotating type. Although the condensing subsystem shown in FIG. 1 has one polarizing element, the concentrating subsystem may have a plurality of polarizing elements. The focusing field stop 125 controls the FOV of the focusing subsystem. The condensing subsystem captures the light from the wafer 120 and directs the light into the condensing optical system 122 and the polarizing element 124 to focus on the condensing field stop 125. In certain embodiments, a converging field stop 125 is used as a spectrometer slit in place of the detector subsystem spectrometer. Nevertheless, the condensing field stop 125 may be disposed at or near the spectroscopic slit 126 of the spectroscope of the detection subsystem.

  The collection subsystem shall have any type and arrangement of collection optics 122, aperture stop 123, polarizing element 124 and field stop 125 known in the field of spectroscopic ellipsometry, reflectometry and scatterometry. be able to.

  In the embodiment shown in FIG. 1, the collection optics subsystem directs light to a plurality of spectrographs provided in the detection subsystem. The detection subsystem generates an output in response to light collected from the structure or structures illuminated by the illumination subsystem.

  A detector subsystem according to one aspect includes two or more detectors each configured to simultaneously detect collected light over several wavelength ranges including infrared.

  In the embodiment shown in FIG. 1, the condensed light 127 passes through the spectroscope slit 126 and is incident on the diffraction element 128. The diffractive element 128 is configured to diffract the first group of wavelengths of the incident light in ± 1st order while diffracting the other group of wavelengths of the incident light in the 0th order. A portion 129 shown in FIG. 1 is a portion including the ultraviolet spectrum of the incident light, and is dispersed toward the detector 141 by the diffraction element 128 with a diffraction order of ± 1. In addition, the diffraction element 128 is configured to reflect the portion 140 including the infrared wavelength in the incident light with a diffraction order of 0 in the direction of the grating 147. The light 140 is incident on the diffractive element 147, and the diffractive element 147 disperses the portion 148 including the infrared wavelength of the incident light 140 with a diffraction order of ± 1 and directs it toward the detector 150.

  In the embodiment shown in FIG. 1, the diffraction element 128 is a reflection grating element. However, in general, the incident light is subdivided into several wavelength bands, the several wavelength bands are propagated along different directions, and one of the wavelength bands is dispersed and any suitable The diffractive element 128 only needs to be configured so as to face the detector in a different form. The diffraction element 128 according to an example is configured as a transmission grating. A diffraction element 128 according to certain other examples includes a beam splitter that subdivides the beam into several wavelength bands, and a reflective or transmissive grating that disperses one of the wavelength bands and directs it toward the detector 141. Structure.

  The reason why the reflection grating 128 is employed is that it exhibits a high ± first-order diffraction efficiency in the ultraviolet spectral region and a high zero-order diffraction efficiency in the infrared spectral region. By adopting the reflection grating, the loss inherent to the beam branch element (for example, dichroic beam branch element) is avoided.

  The diffractive elements 128 and 147 linearize the first-order diffracted light according to the wavelength along the one dimension of the corresponding two-dimensional detector (ie, the wavelength dispersion direction noted in FIG. 1 for the corresponding detector). To disperse. For purposes of illustration, light detected at two wavelengths is shown on the surface of detector 141. The diffractive element 128 generates a spatial separation between the two light wavelengths projected onto the surface of the detector 141. In this way, light collected from the measurement spot 116 having a specific wavelength is projected onto the detector 141 to form the spot 142A, and collected from the measurement spot 116 having another wavelength. Light is projected onto the detector 141 to form a spot 142B.

  The detector 141 according to an example is a charge coupled device (CCD) that is sensitive to ultraviolet and visible light (eg, light having a wavelength of 190 nm to 860 nm). The detector 150 according to an example is a photodetector array (PDA) that is sensitive to infrared light (eg, light having a wavelength of 950 nm to 2500 nm). In general, however, other two-dimensional detector technologies can be envisioned (eg, position sensitive detector (PSD), infrared detector, photovoltaic detector, etc.). Each detector converts incident light into an electrical signal indicative of the spectral intensity of the incident light. For example, the UV detector 141 generates an output signal 154A indicating incident light 129, and the IR detector 150 generates an output signal 154B indicating incident light 148.

  The detection subsystem shown in FIG. 1 is arranged so that the collected light propagates simultaneously to all detectors of the metering system 100. The weighing system 100 also includes an information processing system 130 configured to receive a detection signal 154 including both UV and IR signals and obtain an estimated value of a parameter of interest of the structure (s) to be measured based on both the UV and IR signals. Have. By simultaneously collecting the UV and IR spectra, the measurement time is shortened, and the entire spectrum is measured under the same alignment conditions. Thereby, since a common correction can be applied to all the spectral data sets, the wavelength error can be corrected more easily.

  In a further aspect, a fine focus sensor (FFS) is incorporated into the detection subsystem to provide a focus error correction measurement input during measurement.

  FIG. 2 illustrates another embodiment 200 of a metering system having an FFS 146. Of the elements shown in FIG. 2, those configured similarly to the weighing system 100 shown in FIG. 1 are indicated using the same reference numerals. 2 is diffracted by the diffraction element 128 and is incident on the beam branching element 143. The beam branching element 143 may be transmissive or reflective. The beam branching element 143 directs the portion 145 in the IR region of the light to the IR grating 147 and directs the portion 144 of the light below the IR region (that is, the UV to visible region) to the FFS 146. In this way, UV to visible light diffracted by zero order by the diffraction element 128 is detected by the FFS 146. In certain embodiments, the FFS 146 is a photodiode array, and the beam splitter 143 is a dichroic beam splitter capable of IR high efficiency reflection and UV high efficiency transmission. In certain other embodiments, the beam splitter 143 splits the beam into two or more beams that are neutral intensity filters, partial reflectors, uncoated substrates, etc., and are associated with individual channels and are less intense. Any suitable condensing element.

  An output (not shown) generated by the FFS 146 is sent to the information processing system 130. The information processing system 130 obtains a change in the focal position (z position) of the wafer 120 based on the output of the FFS 146. Any desired focal position change of the wafer 120 is sent to a wafer positioning system (not shown) that adjusts the z position of the wafer 120 accordingly.

  FIG. 3 shows another embodiment 300 of a metering system having an FFS 146. Of the elements shown in FIG. 3, those configured similarly to the weighing system 100 shown in FIG. 1 are indicated using the same reference numerals. The 0th-order diffracted light 149 shown in FIG. 3 is diffracted by the diffractive element 147, and enters the FFS 146, while the first-order diffracted light 148 enters the IR detector 150.

  An output (not shown) generated by the FFS 146 is sent to the information processing system 130. The information processing system 130 obtains a change in the focal position (z position) of the wafer 120 based on the output of the FFS 146. Any desired focal position change of the wafer 120 is sent to a wafer positioning system (not shown) that adjusts the z position of the wafer 120 accordingly.

  A metering system according to another further aspect has two or more detectors configured to simultaneously detect light in different IR spectral ranges.

  FIG. 4 shows another embodiment 400 of a metering system having a plurality of cascaded IR detectors. Of the elements shown in FIG. 4, those configured similarly to the weighing system 100 shown in FIG. 1 are indicated using the same reference numerals. As shown in FIG. 4, the light 145 enters the IR grating 147. The IR grating 147 is configured to first-order diffract a portion 148 of the incident light 145. The first-order diffracted light 148 includes a part of the IR wavelength region of the incident light 145. Further, the IR grating 147 is configured to diffract the portion 149 of the incident light 145 in the 0th order. The zero-order diffracted light 149 includes an IR wavelength that is outside the IR wavelength range composing the first-order diffracted light 148. The zero-order diffracted light 149 propagates to the IR grating 151, and the IR grating causes the incident light to be first-order diffracted and directed to the IR detector 153. The first order diffracted light 152 in the embodiment shown in FIG. 4 includes all IR wavelengths of the incident light 149. On the other hand, in certain other embodiments, the IR grating 151 is configured to first-order diffract only a portion of the incident light, and the remaining zeroth-order light is further directed to other IR gratings. In this way, an arbitrary number of IR detectors can be connected in cascade, and the individual IR wavelength region of the condensed light 127 can be detected.

  The embodiments described with reference to FIGS. 1-4 are presented with non-limiting examples, and many other configurations for simultaneous detection of UV, visible and IR wavelengths can be envisaged. According to an example, the IR wavelength of the collected light 127 is dispersed by first-order diffraction, and the UV wavelength of the collected light 127 is zero-order diffracted and directed toward the UV grating and the detector. The system can be configured. By employing a beam branching element according to a certain example, the entire spectrum of the condensed light can be subdivided into two or more sub-spectrums. Nevertheless, it may be beneficial to employ a diffractive element as described herein, thereby avoiding the loss associated with beam branching elements such as dichroic beam splitters, neutral density filters, partial reflectors or uncoated substrates. can do.

  The illumination light beam 117 shown in FIG. 1 is supplied to the surface of the wafer 120 at an oblique angle. In general, the illumination light can be supplied to the surface of the wafer 120 at any oblique angle and any number of oblique angles. In certain embodiments, the illumination light group is supplied to the surface at normal incidence (ie, aligned with the surface normal) in addition to oblique illumination.

  As shown in FIG. 1, the Z axis is oriented in a direction perpendicular to the surface of the wafer 120. The X and Y axes are in the same plane as the surface of the wafer 120 and are therefore perpendicular to the Z axis. The incident surface is determined by the principal ray 118 of the illumination light beam 117 and the principal ray 121 of the condensed light beam 127. The X axis is aligned with the entrance surface, and the Y axis is orthogonal to the entrance surface. In this configuration, the incident surface exists in the XZ plane. The illumination light beam 117 is incident on the surface of the wafer 120, and the incident angle with respect to the Z axis is α and exists in the incident surface. Since the shape projection of the illumination light beam onto the specimen surface is performed at an oblique angle, the illumination beam cross section along the direction aligned with the incident surface is elongated. By way of non-limiting example, since the circular illumination light beam is projected onto the wafer surface, the illumination area is elliptical. Thus, generally, the oblique illumination of the surface produces a projected illumination area that is longer than the illumination cross section, and the lengthening direction is the direction aligned with the incident surface. Furthermore, the greater the incident angle, the greater the degree of lengthening. More specifically, the beam shape is inversely proportional to the cosine value of the incident angle along the direction of the incident surface. In the absence of diffraction and aberration effects, the projection illumination light remains undistorted along a direction perpendicular to the illumination plane (eg, the Y direction).

  FIG. 5A is a top view of wafer 120 including an illustration of measurement spot 116 illuminated by illumination light beam 117 of FIG. In the embodiment shown in FIG. 1, the section of the illumination light beam 117 is circular (eg, at the illumination field stop 113). In the case of a circular illumination light beam, the measurement spot 116 resulting from the projection onto the surface of the wafer 120 is elliptical as shown in FIG. 5A.

  The measurement spot 116 shown in FIG. 1 is projected onto the surfaces of the detectors 141 and 150 in a wavelength dispersive manner. Moreover, in a certain aspect, the spectroscopic member of the measurement system described in the present application is configured so that the plane of light dispersion on each detector is oriented in a direction perpendicular to the projection of the incident surface on each detector. In this configuration, the measurement spot 116 is imaged on each detector so that the direction aligned with the incident surface on the wafer surface is directed to the direction perpendicular to the wavelength dispersion direction on the detector surface. Such an arrangement greatly reduces the sensitivity of the weighing system to focus errors. Since the sensitivity to the focusing error is low, a precise measurement result can be obtained with a shorter MAM time and therefore with a higher throughput. A significant advantage of this architecture is the ability to measure thick film and multilayer stacks without incurring wavelength errors.

  Conventionally, the measuring system is configured so that the projection in the longitudinal direction of the measurement spot is aligned with the chromatic dispersion direction on the detector surface. FIG. 5B shows a conventional configuration. As shown in FIG. 5B, the projection of the measurement spot 116 in the longitudinal direction (that is, the X axis on the wafer and the X ′ axis on the detector) onto the detector 23 is the direction of chromatic dispersion on the surface of the detector 23. Are aligned. For example, the long direction of the spots 24A and 24B is aligned with the chromatic dispersion direction. By integrating these wavelength-dependent images (eg, spots 24A and 24B) on the surface of the detector 23 along the direction perpendicular to the chromatic dispersion direction, the spectrum, that is, the intensity as a function of the wavelength along the chromatic dispersion axis is obtained. can get. In the case of a CCD detector, the spectrum is produced by integrating the charge along a direction perpendicular to the chromatic dispersion.

  When the measurement spot is imaged on the detector so that the direction aligned with the incident surface on the wafer surface is aligned with the chromatic dispersion direction on the detector surface, the resulting point spread function (PSF) is strongly wavelength dependent. Exhibits sex. The resulting PSF exhibits a high peak because the image intensity varies greatly along the lengthwise direction for a given wavelength. In order to accurately capture this high peak PSD, the spectral data must be captured with high resolution by a spectrometer. Therefore, the measurement time is extended and the throughput is lowered.

  Also, for example, when a long image and a corresponding long intensity distribution are aligned in the direction of spectral dispersion, the PSF provided for a specific wavelength depends on the incident angle. The resulting PSF expands or narrows depending on the incident angle.

  Also, for example, the resulting PSF is highly sensitive to focus errors. As the measurement target on the wafer moves or is out of focus, the detection image of the measurement spot on the wafer changes in size or shifts in position. In addition, the position of the measurement spot on the wafer is shifted. As shown in FIG. 6, when the wafer 120 is in focus, the illumination light beam 117 illuminates the portion A of the wafer. When the condensed light beam 127 is wavelength-dispersed and imaged on the detector 23 in the conventional form, the image appears in the spots 24A and 24B as shown in FIG. When the wafer 120 moves upward along the z direction and is defocused by an amount ΔZ exceeding 0, the illumination light beam 117 illuminates the portion C of the wafer. When the focused light beam 127 ′ is wavelength-dispersed and imaged on the detector 23 in the conventional form, the image appears in the spots 24 </ b> A ′ and 24 </ b> B ′. The appearing image becomes larger as the wafer moves away from the focal plane of the optical system, and the center position of the image shifts along the direction aligned with the chromatic dispersion direction. Due to this shift along the chromatic dispersion direction, the wavelength-to-pixel mapping changes, which causes a spectrum measurement error. When the wafer 120 moves downward along the z direction and is defocused by an amount ΔZ of less than 0, the portion B of the wafer is illuminated by the illumination light beam 117. When the focused light beam 127 "is wavelength-dispersed and imaged on the detector 23 in the conventional form, the image appears at the spots 24A" and 24B ". Again, the wafer is separated from the focal plane of the optical system. As the image becomes larger, the center position of the image shifts along the direction aligned with the wavelength dispersion direction.

  In such a situation, the movement of the measurement spot on the wafer 120 caused by the focusing error ΔZ ≠ 0 causes image movement along the spectrometer dispersion axis as a function of wavelength. Wavelength calibration is performed on the in-focus plane, ie Z = 0, so if there is any image movement along the spectrometer dispersion direction caused by the focus error, the measurement spectrum is very sensitive to deviations from the wavelength calibration become.

  On the other hand, by projecting the incident surface onto the detector perpendicular to the chromatic dispersion direction as described in this application, the dispersion plane is separated from the incident surface, so that the focusing error is the spectral position on the detector. No longer affect.

  As shown in FIG. 1, the measurement spot 116 is projected onto the surface of the detector 141 and the detector 150 in a chromatic dispersion form. The weighing system 100 is configured such that the projection in the longitudinal direction of the measurement spot 116 is directed in a direction perpendicular to the chromatic dispersion direction on the surfaces of the detectors 141 and 150. The X ′ axis shown in FIG. 1 represents the projection of the measurement spot 116 in the longitudinal direction (that is, the X axis) onto the detectors 141 and 150. The X ′ axis shown in FIG. 1 is oriented in a direction perpendicular to the chromatic dispersion direction on the surfaces of the detectors 141 and 150.

  According to certain examples, the measurement spot is imaged onto the detector such that the direction aligned with the entrance plane on the wafer surface is oriented perpendicular to the chromatic dispersion direction on the detector surface. Thus, a 20-fold reduction in sensitivity to the focal position is achieved. By reducing the focus error sensitivity, it is possible to reduce the focus accuracy and reproducibility conditions, increase the focusing time, and reduce the sensitivity to wavelength errors without degrading the measurement accuracy. These effects are especially evident in large numerical aperture optical metering systems.

  FIG. 8 is a direct view of the surface of the detector 141. As shown in FIG. 8, the projection in the longitudinal direction of the measurement spot 116 (that is, the X ′ axis) is directed in a direction perpendicular to the chromatic dispersion direction on the surface of the detector 141. For example, the long direction of the spots 142A and 142B is oriented in a direction perpendicular to the wavelength dispersion direction. By integrating these wavelength-dependent images (eg, spots 142A and 142B) on the surface of the detector 141 along the direction perpendicular to the chromatic dispersion direction, the spectrum, that is, the intensity as a function of the wavelength along the chromatic dispersion axis, is obtained. can get. In the case of a CCD detector, the spectrum is produced by integrating the charge along a direction perpendicular to the chromatic dispersion.

  A measurement spectrum is obtained by integrating the image projected on the surface of the detector (eg, CCD 141) along the direction perpendicular to the wavelength dispersion axis of the spectrometer at each wavelength. The individual spectral shape at each wavelength is the point spread function (PSF) of the system at that particular wavelength.

  The point spread function (PSF) that results when the measurement spot is imaged on the detector such that the direction aligned with the entrance plane on the wafer surface is oriented perpendicular to the chromatic dispersion direction on the detector surface. Is much less dependent on the wavelength than the conventional configuration. The resulting PSF exhibits a low peak because the image intensity does not vary so much along the direction perpendicular to the long direction for a given wavelength (eg, along the minor axis of the ellipse). Further, although the image intensity varies greatly along the long direction (eg, along the long axis of the ellipse), such variation is integrated and smoothed because the long direction is aligned with the charge integration direction of the CCD. According to this configuration, it is not necessary to capture the spectral data with high resolution by the spectroscope and accurately construct the PSF. Therefore, measurement time is shortened and throughput is increased.

  Also, for example, when a long image is oriented in a direction perpendicular to the direction of spectral dispersion, the PSF produced for a particular wavelength is independent of the incident angle. The image and the corresponding intensity distribution along the direction perpendicular to the longitudinal direction (ie, along the minor axis of the ellipse) are generally invariant with respect to the incident angle. In other words, the image and the intensity distribution corresponding to the image, and those obtained by projection along the spectral dispersion direction are substantially unchanged with respect to the incident angle. Therefore, the calculated PSF has almost no dependence on the incident angle.

  Also, for example, the resulting PSF exhibits a much lower sensitivity to focus error compared to conventional configurations. As the measurement target on the wafer moves or is out of focus, a position shift occurs in the detection image of the measurement spot on the wafer. Similar to that shown in FIG. 6, when the wafer 120 is in focus, the illumination light beam 117 illuminates the portion A of the wafer. The condensed light beam 127 is wavelength-dispersed and forms an image on the detector 141 as spots 142A and 142B as shown in FIG. When the wafer 120 moves upward along the z direction and is defocused by an amount ΔZ exceeding 0, the illumination light beam 117 illuminates the portion C of the wafer. The condensed light beam 127 ′ is wavelength-dispersed and imaged on the detector 141 as spots 142 A ′ and 142 B ′. In this image position shift perpendicular to the chromatic dispersion direction, the wavelength-to-pixel mapping does not change, so the spectral measurement error induced by the focusing error is reduced. When the wafer 120 moves downward along the z direction and is defocused by an amount ΔZ of less than 0, the portion B of the wafer is illuminated by the illumination light beam 117. The condensed light beam 127 "is wavelength-dispersed and forms an image on the detector 141 in the form of spots 142A" and 142B ". Also at this time, the image position shift is perpendicular to the wavelength dispersion direction. The spectral measurement error induced by the focusing error is reduced.

  In this configuration, the image on the detector is shifted along the direction perpendicular to the wavelength dispersion axis due to the focusing error. Since the calculated spectrum is obtained by integrating the image perpendicular to the spectroscopic dispersion axis, the image shift induced by the focusing error is integrated and smoothed and does not induce a substantial spectrum measurement error. This reduction in sensitivity to focusing error eliminates the need to track and correct focusing error based on atomic beam radiation. In this configuration, a broadband light source, such as a high intensity laser driven light source (LDLS), can be employed as a spectroscopic system, such as a light source in the system 100, under mild focus positioning conditions.

  As described above, the PSF caused by the projection by the spectroscope is almost determined by the light distribution along the direction perpendicular to the incident surface (that is, the XZ plane). That is why PSF is independent of the oblique incident angle. That is, the wavelength dependence of PSF is considerably less than that of the conventional configuration.

  As described herein, in any normal or oblique incidence broadband optical metrology system, the measurement spot is imaged on the detector surface such that the direction aligned with the entrance surface on the wafer surface is It can be configured to face a direction perpendicular to the chromatic dispersion direction on the detector surface. By directing the spectrometer dispersion axis in a direction perpendicular to the wafer focus axis (eg, the z-axis in FIGS. 1-4) according to certain embodiments, the system sensitivity to focus errors can be further reduced. .

  In some embodiments, multi-zone infrared detectors that combine several sensitivity bands at different locations on a single detector package are employed in the metering system described herein. The detector is configured to provide continuous spectrum data with different sensitivities depending on the location of incidence.

  FIG. 10 shows a typical photosensitivity curve for an available indium gallium arsenide (InGaAs) sensor. As shown in FIG. 10, none of the available InGaAs sensors can provide appropriate photosensitivity over a wavelength band of 1 μm to 2.5 μm. That is, when viewed individually, the available sensors can only sense across a narrow waveband. In some embodiments, the individual sensors are arranged in a cascade arrangement as shown in FIG. 4, for example. However, in that case, the collected light can be subdivided into individual spectral regions by means of individual grating structures or a combination of beam splitters and grating structures, and each spectral region can be distributed onto a separate detector. It is necessary to make it. The result is unnecessary light loss and optical system complexity.

  In one embodiment, a plurality of sensor chips sensitive to different wave bands are combined to form a single detector package. In addition, the multi-zone detector is mounted in the metering system described herein.

  FIG. 9 shows the composition of the multi-zone infrared detector 150 which is four sensor chips 150A to 150D derived from four different wavebands. As shown in FIG. 10, these four sensor chips have different material compositions that exhibit different photosensitivity characteristics. As shown in FIG. 10, the sensor chip 150A exhibits high sensitivity in the wave band A, the sensor chip 150B exhibits high sensitivity in the wave band B, and the sensor chip 150C exhibits high sensitivity in the wave band. Within C, it is within waveband D that sensor chip 150D exhibits high sensitivity. The weighing system incorporating the detector 150 disperses the wavelength in the waveband A onto the sensor chip 150A, disperses the wavelength in the waveband B onto the sensor chip 150B, and detects the wavelength in the waveband C as a sensor. It is configured to disperse onto the chip 150C and disperse the wavelengths in the waveband D to the sensor chip 150D. By doing in this way, high photosensitivity (namely, high SNR) is implement | achieved by a single detector over the integrated waveband containing wavebands AD.

  A multi-zone detector according to certain examples has an InGaAs sensor that is sensitive to different spectral regions, assembled into a single sensor package, so that 750 nm to 3000 nm or even more A single and constant spectrum covering the outer wavelengths can be obtained.

  In general, no matter how many individual sensors are assembled along the chromatic dispersion direction of the multi-zone detector, a continuous spectrum can be obtained from the detector. However, typically two to four individual sensors are employed in a multi-zone detector, such as detector 150.

  According to another further aspect, the measurement accuracy and speed obtained can be optimized based on the properties of the target under measurement by adjusting the dimensions along the plane orthogonal to the incident plane of the projection on the wafer plane of the illumination field stop. it can.

  By adjusting the projection on the wafer plane of the illumination field stop along the direction perpendicular to the incident plane, the PSF can be shaped for each measurement application so that a flat top profile that is hardly sensitive to wavelength is achieved. In addition, by adjusting the spectral resolution, measurement accuracy and speed can be optimized based on the flat top profile.

  According to a certain example, for example, when the sample is a very thick film or a grating structure, by adjusting the projection on the wafer plane of the illumination field stop along the direction orthogonal to the incident surface, the field size is suppressed and the spectral resolution is reduced. Can improve. According to a certain example, for example, when the sample is a thin film, the projection time on the wafer plane of the illumination field stop is adjusted along the direction orthogonal to the incident plane, thereby widening the field size and measuring time without loss of spectral resolution. Can be shortened.

  In the embodiment illustrated in FIGS. 1-4, the information processing system 130 is configured to receive a signal 154 indicative of the spectral response detected by the detectors 141, 150, and 153 (if applicable). The information processing system 130 is further configured to determine the control signal 119 and send it to the programmable illumination field stop 113. The programmable illumination field stop 113 receives the control signal 119 and adjusts the size of the illumination aperture so that the desired illumination field size is achieved.

  According to certain examples, the measurement accuracy and speed can be optimized as described above by adjusting the illumination field stop. Further, according to an example, by adjusting the illumination field stop, it is possible to prevent image clipping due to the spectroscopic slit and measurement result deterioration corresponding thereto. In this case, the illumination field size is adjusted so that the spectroscope slit is not filled with the image of the measurement target. In one example, the illumination field stop is adjusted so that the projection of the polarizer slit of the illumination optics does not fill the spectroscope slit of the metering system.

  FIG. 11 shows a spectroscopic measurement execution method 500 according to at least one aspect. The method 500 is suitable for implementation in a weighing system, for example, the weighing systems 100, 200, 300 and 400 of the present invention shown in FIGS. According to an aspect, the methods 500 may be implemented by executing pre-programmed algorithms by one or more processors included in the information processing system 130 or any other general purpose information processing system so that it can be recognized. Data processing blocks can be executed. As recognized in this application, certain structural aspects of the metering systems 100, 200, 300 and 400 are not to be construed as limiting but are to be construed solely as examples.

  In block 501, the group of broadband illumination light from the illumination source is directed to a measurement spot on the surface of the sample under measurement at one or more incident angles within the incident surface.

  In block 502, a group of light is collected from a measurement spot on the specimen surface.

  In block 503, the first portion in the first wavelength region of the condensed light group is directed to the surface of the first detector, and the second portion in the second wavelength region of the condensed light group is directed to the second detector. To the surface.

  In block 504, a response of the specimen to the illumination light group in the first wavelength range is detected.

  In block 505, the response of the sample to the illumination light group in the second wavelength range is detected at the same time as the response of the sample to the illumination light group in the first wavelength range is detected.

  Examples of measurement techniques that can be configured as described herein include, but are not limited to, spectroscopic ellipsometry (SE) such as Mueller matrix ellipsometry (MMSE), rotating polarizer SE (RPSE), rotating polarizer rotation Compensator SE (RPRC), rotation compensator rotation compensator SE (RCRC), spectral reflectometry (SR) such as polarized SR, non-polarized SR, spectral scatterometry, scatterometry overlay, beam profile reflectometry, angle resolution or There are polarization-resolved beam profile ellipsometry, single or multiple discrete wavelength ellipsometry, and so on. In general, any metrology that includes illumination with UV and IR wavelengths can be envisaged individually or in any combination. For example, any SR or SE technology applicable to semiconductor structure characterization, including image-based metrology, can be envisaged individually or in any combination.

  The systems 100, 200, 300, and 400 according to further embodiments use one or a plurality of information processing systems 130, and measure an actual device structure based on spectroscopic data collected according to the method described in the present application. It is something to execute. The one or more information processing systems 130 may be communicatively coupled to the spectrometer. In one aspect, one or more information processing systems 130 are configured to receive measurement data 154 related to measurement of the structure of the specimen 120.

  It should be appreciated that one or more of the steps described throughout this disclosure may be performed by a single computer system 130 or alternatively by a multiple computer system 130. . Further, the various subsystems of the systems 100, 200, 300 and 400 may include computer systems suitable for performing at least some of the steps described herein. Accordingly, the above description should not be construed as limiting the invention but merely as exemplifications.

  In addition, the computer system 130 may be communicatively coupled to the spectrometer in any form known in the art. For example, one or a plurality of information processing systems 130 can be coupled to an information processing system related to a spectroscope. Also, for example, the spectrometers can be controlled directly by a single computer system coupled to computer system 130.

  The computer system 130 of the weighing systems 100, 200, 300 and 400 receives and / or receives data or information from a transmission medium such as a wired section and / or a wireless section thereof (eg, a spectrometer, etc.). It may be configured so that it can be captured. In this configuration, the transmission medium can serve as a data link between the computer system 130 and the other subsystems of the systems 100, 200, 300, and 400.

  The computer system 130 of the weighing systems 100, 200, 300 and 400 has a transmission medium such as a wired section and / or a wireless section, whereby data or information (eg, measurement results, modeling inputs, modeling results, reference measurement results) from other systems. Etc.) may be received and / or captured. In this configuration, the transmission medium serves as a data link between the computer system 130 and other systems (eg, on-board memory, external memory or other external systems of the weighing systems 100, 200, 300 and 400). Can do. For example, the information processing system 130 may be configured to receive measurement data from a storage medium (that is, the memory 132 or an external memory) via a data link. For example, the spectroscopic result acquired using the spectroscope described in the present application may be stored in a permanent or semi-permanent storage device (eg, the memory 132 or an external memory). According to this configuration, the spectral result can be imported from the on-board memory or from the external memory system. Further, the computer system 130 may send data to other systems via a transmission medium. For example, an estimated parameter value obtained by the measurement model or the computer system 130 may be sent and stored in an external memory. According to this configuration, the measurement result can be exported to another system.

  The information processing system 130 can include, but is not limited to, a personal computer system, a mainframe computer system, a workstation, an image computer, a parallel processor, and any other device known in the art. In general, the term “information processing system” can be broadly defined to include all devices having one or more processors that execute instructions obtained from a storage medium.

  The program instructions 134 for performing the method, eg, that described herein, may be transmitted over a transmission medium, such as a wire, cable, or wireless transmission link. For example, as depicted in FIG. 1, program instructions 134 stored in memory 132 are transmitted over bus 133 to processor 131. Program instructions 134 are stored in a computer readable medium (eg, memory 132). Examples of computer readable media include read only memory, random access memory, magnetic or optical disk and magnetic tape.

  In certain examples, the metrology model is implemented as a component of a SpectraShape optical critical dimension metrology system available from KLA-Tencor Corporation of Milpitas, California. In this configuration, a model is generated and prepared for use immediately after the spectrum is collected by the system.

  In another type of example, the measurement model is realized off-line by executing AcuShape (registered trademark) software available from, for example, KLA-Tencor Corporation of Milpitas, California, USA, by an information processing system. The resulting trained model can be incorporated as a component of an AcuShape® library that can be accessed by the metrology system that performs the measurements.

  Also, in certain aspects, the semiconductor device spectrometric methods and systems described herein are applied to the measurement of high aspect ratio (HAR) structures, large lateral dimension structures, or both. Examples of structures suitable for measurement by the systems and methods described herein include a three-dimensional NAND structure such as a vertical NAND (V-NAND (registered trademark)) structure, a dynamic random access memory structure (DRAM), and the like. Semiconductor manufacturers such as Samsung Inc. (Korea), SK Hynx Inc. (Korea), Toshiba Corporation (Japan), Micron Technology, Inc. (US) etc. Such a complicated device has a problem of low translucency into the structure (group) to be measured. FIG. 12 shows an example 600 of a high aspect ratio NAND structure that has a problem of low transmissivity into the structure (group) to be measured. A spectroscopic ellipsometer having a broadband capability extending to the infrared and performing simultaneous spectral band detection with a multi-zone sensor as described in the present application is suitable for measurement of such a high aspect ratio structure.

  According to yet another aspect, the measurement results described herein can be used to provide active feedback to a processing tool (eg, lithography tool, etching tool, deposition tool, etc.). For example, measurement parameter values derived by relying on the measurement methods described herein can be sent to the lithography tool and the lithography system can be adjusted to obtain the desired output. Similarly, etching parameters (eg, etching time, diffusivity, etc.) and deposition parameters (eg, time, concentration, etc.) can be incorporated into the measurement model, and active feedback can be applied to the etching tool and the deposition tool, respectively. According to an example, corrections to the processing parameters determined based on the trained metrology model as well as the device parameter measurements can be sent to the lithography tool, etching tool or deposition tool.

  As used herein, the term “critical dimension” includes any critical dimension of the structure (eg, lower critical dimension, middle critical dimension, upper critical dimension, sidewall angle, grid height, etc.), and the limit between any two or more structures. Dimensions (eg, distance between two structures), as well as misalignment between two or more structures (eg, overlay misregistration between overlapping lattice structures, etc.) are encompassed. Examples of structures include a three-dimensional structure, a structure with a pattern, and an overlay structure.

  The term “limit dimension application” or “limit dimension measurement application” described in this application encompasses all critical dimension measurements.

  As used herein, the term “weighing system” is at least partially employed to characterize specimens in any manner, including metrology applications such as critical dimension metrology, overlay metrology, focus / dose metrology, and composition metrology. All systems are included. Nonetheless, these technical terms do not limit the scope of the word “metering system” described herein. In addition, the metrology system 100 can be configured for metrology of patterned and / or unpatterned wafers. This weighing system can be LED inspection tools, edge inspection tools, back inspection tools, macro inspection tools or multi-mode inspection tools (with simultaneous data acquisition from one or more platforms) and system parameters based on critical dimension data It can be configured as any other weighing or inspection tool that benefits from the calibration of

  Various embodiments are described herein with respect to a semiconductor metrology system that can be used to measure a specimen within any semiconductor processing tool (eg, inspection system or lithography system). In this application, the term “specimen” is used to refer to any sample such as a wafer, reticle or other material that can be processed (eg, printed or tested for defects) by means known in the art.

  The term “wafer” in this application generally refers to a substrate formed of a semiconductor or non-semiconductor material. Examples of the material include, but are not limited to, single crystal silicon, gallium arsenide, and indium phosphide. Such substrates are often seen and / or processed in semiconductor manufacturing facilities. In some cases, the wafer may be composed only of a substrate (so-called bare wafer). Instead, the wafer may have one or more layers, which are formed of different materials on the substrate. One or more layers formed on the wafer may be “patterned” or “unpatterned”. For example, a plurality of dies having repeatable pattern features may exist in the wafer.

A “reticle” may be a reticle at any stage of the reticle manufacturing process or a finished product of the reticle, and may or may not be released for use in a semiconductor manufacturing facility. A reticle or “mask” is generally defined as a substantially transparent substrate having a substantially opaque area formed thereon, the area being patterned. The substrate may contain, for example, a glass material such as amorphous SiO ₂ . By arranging the reticle on the resist-coated wafer and performing an exposure step in the lithography process, the pattern on the reticle can be transferred to the resist.

  One or more layers formed on the wafer may be patterned or unpatterned. For example, a repeatable pattern feature can be provided on each of a plurality of dies constituting a wafer. By forming and processing such a material layer, a final device can be finally obtained. Many types of devices can be formed on a wafer, and the term wafer in this application is intended to encompass a wafer on which any type of device known in the art is fabricated. .

  According to one or more exemplary embodiments, the functions described above can be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions are stored on or transmitted over a computer readable medium as one or more instructions or code. Computer-readable media includes both computer storage media and communication media, as well as all media useful for transferring a computer program from one place to another. The storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example and not limitation, such computer readable media may be any desired form of instruction or data structure, including RAM, ROM, EEPROM, CD-ROM and other optical disk storage, magnetic disk storage and other magnetic storage devices. Any other medium that can be used to carry or store the program code means and that can be accessed by a general purpose or special purpose computer or a general purpose or special purpose processor can be constructed. In addition, any connection may be referred to as a computer-readable medium. For example, if software is transmitted from a website, server or other remote source, coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology such as infrared, radio frequency or microwave is used. These coaxial cables, fiber optic cables, twisted pairs, DSL or wireless technologies such as infrared, radio frequency or microwave fall within the definition of the medium. The term disk / disc in this application includes compact discs (CD), laser discs, optical discs, digital versatile discs (DVD ™), floppy discs, and Blu-ray ™ discs, usually data. Includes a disk that is magnetically reproduced and a disk that is optically reproduced by a laser. Combinations of the above should also be included within the scope of computer-readable media.

  Although specific embodiments have been described above for teaching purposes, the teachings of the present patent application have general applicability and are not limited to the specific embodiments described above. Accordingly, various modifications, adaptations, and combinations can be made to the features of the above-described embodiments without departing from the technical scope of the present invention as set forth in the claims.

Claims (24)

One or more illumination sources configured to generate a broadband illumination light group;
An illumination optics subsystem configured to direct a group of illumination light from an illumination source to a measurement spot on the surface of the sample under measurement at one or more angles of incidence within a plane of incidence;
A collection optics subsystem configured to collect a collection of collected light from a measurement spot on the surface of the specimen;
A first detector having a flat, two-dimensional surface sensitive to incident light, the first detector configured to detect a response of the sample to a group of illumination light in the first wavelength range;
A second detector having a flat and two-dimensional surface that is sensitive to incident light, the response of the sample to the illumination light group in the second wavelength range, and the sample to the illumination light group in the first wavelength range. A second detector configured to detect simultaneously with the response of
A first diffractive element configured to disperse a first portion in the first wavelength region of the collected light group toward the surface of the first detector;
A second diffractive element configured to disperse a second portion in the second wavelength region of the collected light group toward the surface of the second detector;
A weighing system comprising.   2. The metering system according to claim 1, wherein a direction aligned with an incident surface projected on the first detector is a direction perpendicular to a direction of chromatic dispersion on the surface of the first detector. A metering system in which the collection optics subsystem images the measurement spot onto the surface of the first detector.   3. The metering system according to claim 2, wherein the direction aligned with the incident surface projected onto the second detector is oriented perpendicular to the direction of chromatic dispersion on the surface of the second detector. A metering system in which the collection optics subsystem images the measurement spot onto the surface of the second detector.   2. The metering system according to claim 1, wherein the second detector has two or more different surface areas each exhibiting different light sensitivities, and the two or more different surface areas are the second detector. Weighing system aligned in the direction of chromatic dispersion across the surface. The weighing system of claim 1, further comprising:
A third detector having a flat and two-dimensional surface that is sensitive to incident light, the response of the sample to the illumination light group in the third wavelength range, and the sample to the illumination light group in the first wavelength range. A third detector configured to detect simultaneously with the response of
A third diffractive element configured to disperse a third portion in the third wavelength region of the collected light group toward the surface of the third detector;
A weighing system comprising. The weighing system of claim 1, further comprising:
A fine focus sensor configured to detect a portion of the collected light group;
A beam branching element configured to direct the part of the condensed light group to the fine focus sensor, and the first and second detectors detect the response of the sample to the illumination light group. At the same time the sample focusing error is detected,
Weighing system.   The weighing system according to claim 1, wherein the illumination light group is broadband illumination light having a wavelength range including infrared, visible, and ultraviolet wavelengths.   The weighing system according to claim 1, wherein at least a part of the illumination light group is supplied to the specimen at a normal incidence angle.   The weighing system according to claim 1, wherein at least a part of the illumination light group is supplied to the specimen at an oblique incident angle.   The weighing system according to claim 1, wherein the weighing system is configured as one or more of a spectroscopic ellipsometer and a spectroscopic reflectometer.   2. A weighing system according to claim 1, wherein the sample under measurement is a high aspect ratio weighing target.   2. The weighing system according to claim 1, wherein the sample under measurement has a three-dimensional NAND structure or a dynamic random access memory structure. The weighing system of claim 1, further comprising:
A weighing system including an information processing system configured to generate an estimated value of a target parameter of a sample under measurement based on a combined analysis of outputs of first and second detectors. One or more illumination sources configured to generate a broadband illumination light group;
An illumination optics subsystem configured to direct a group of illumination light from an illumination source to a measurement spot on the surface of the sample under measurement at one or more angles of incidence within a plane of incidence;
A collection optics subsystem configured to collect a collection of collected light from a measurement spot on the surface of the specimen;
A first detector having a flat, two-dimensional surface that is sensitive to incident light, the first detector configured to detect a response of a specimen to a group of illumination light in a first wavelength region, and having different light sensitivities A first detector having two or more different surface areas each of which is aligned in a chromatic dispersion direction across the surface of the first detector;
A first diffractive element configured to disperse a first portion in the first wavelength region of the collected light group past the surface of the first detector;
A weighing system comprising. 15. The weighing system according to claim 14, further comprising:
A second detector having a flat and two-dimensional surface that is sensitive to incident light, the response of the sample to the illumination light group in the second wavelength range, and the sample to the illumination light group in the first wavelength range. A second detector configured to detect simultaneously with the response of
A second diffractive element configured to disperse a second portion in the second wavelength region of the collected light group past the surface of the second detector;
A weighing system comprising.   15. The metering system according to claim 14, wherein the direction aligned with the incident surface projected on the first detector is oriented perpendicular to the direction of chromatic dispersion on the surface of the first detector. A metering system in which the collection optics subsystem images the measurement spot onto the surface of the first detector. 15. The weighing system according to claim 14, further comprising:
A third detector having a flat and two-dimensional surface that is sensitive to incident light, the response of the sample to the illumination light group in the third wavelength range, and the sample to the illumination light group in the first wavelength range. A third detector configured to detect simultaneously with the response of
A third diffractive element configured to disperse a third portion in the third wavelength region of the collected light group past the surface of the third detector;
A weighing system comprising. 15. The weighing system according to claim 14, further comprising:
A fine focus sensor configured to detect a portion of the collected light group;
A beam branching element configured to direct the portion of the collected light group to the fine focus sensor;
A weighing system comprising.   15. The weighing system according to claim 14, wherein the sample under measurement has a three-dimensional NAND structure or a dynamic random access memory structure. Directing a group of broadband illumination light from an illumination source to a measurement spot on the surface of the sample under measurement at one or more incident angles within a certain incident surface;
Condensing a focused light group from a measurement spot on the surface of the specimen;
The first portion in the first wavelength region of the collected light group is directed toward the surface of the first detector, and the second portion in the second wavelength region of the condensed light group is directed to the surface of the second detector. Step to direct,
Detecting a response of the specimen to the illumination light group in the first wavelength range;
Detecting the response of the sample to the illumination light group in the second wavelength range simultaneously with the detection of the response of the sample to the illumination light group in the first wavelength range;
Having a method. The method of claim 20, further comprising:
The measurement spot is placed on the surface of the first detector so that the direction aligned with the incident surface projected onto the first detector is oriented in a direction perpendicular to the direction of chromatic dispersion on the surface of the first detector. Having a step of imaging.   21. The method of claim 20, wherein the second detector has two or more different surface areas each exhibiting different light sensitivities, the two or more different surface areas of the second detector. A method of aligning in the direction of chromatic dispersion across the surface. The method of claim 20, further comprising:
Directing a third portion of the collected light group in the third wavelength region to the surface of the third detector;
Detecting the response of the sample to the illumination light group in the third wavelength range simultaneously with the detection of the response of the sample to the illumination light group in the first wavelength range;
Having a method. 21. The method of claim 20, wherein the sample under measurement is a three-dimensional NAND structure or a dynamic random access memory structure.